Nasal congestion is characteristic of several diseases including the common cold, allergic rhinitis, sinusitis and hay fever. Nasal congestion is caused by dilation of the blood vessels of the nasal mucosa, which leads to swelling of the tissue lining the nasal cavity. The blood vessels of the nasal mucosa are rich in adrenergic receptors. Among the commonly used topical nasal decongestants that act by adrenergic stimulation are the imidazoline derivatives naphazoline, oxymetazoline, xylometazoline and tetrahydrozoline. These adrenergic stimulants constrict the blood vessels in the nasal mucosa and thus relieve the swelling of the nasal tissues.
A number of side effects are associated with use of these agents. For example, oxymetazoline and naphazoline often cause irritation of the nasal mucosa. Excessive or prolonged use of topical nasal decongestants may cause rebound congestion or rhinitis medicamentosa. Rebound congestion or rhinitis medicamentosa is a condition whereby congestion is reduced initially but is followed by a rebound of greater nasal stuffiness that is not relieved when further doses of decongestant are administered. Further, if the topical decongestants are systematically absorbed, side effects may include insomnia, headache, nausea, irritability, dizziness, perspiration, hypertension, tachycardia, palpitations and cardiac arrhythmias.
Thus, a compound with good topical decongestant activity and reduced potential for nasal irritation and other side effects is desirable.